Tool for rolling internal threads



Dec. 25, 1962 P. A. KOEHLER TOOL FOR ROLLING INTERNAL THREADS OriginalFiled Nov. 18, 1955 3 Sheets-Sheet l Dec; 25, 1962 P. A. KOEHLER3,069,939 TOOL FOR ROLLING INTERNAL mamas Original Filed Nov. 18, 1955 sSheets-Sheet 2 INVENTOR. PAM/4 AZ Kay/415R 1952 P. A. KOEHLER 3,069,939

TOOL FOR ROLLING INTERNAL THREADS Original Filed Nov. 18, 1955 3Sheets-Sheet 3 INVENTOR. P40; 9. K05; 1?

United States Patent ()fiFice 3,059,939 Patented Dec. 25, 1962 3 069 939TGDL FOR ROLLIA G INTERNAL THREADS Paul Anthony Koehler, Lyndhurst,Ohio; Marian Elizabeth Kcehler, executrix of said Paul Anthony Koehler,deceased Continuation of abandoned application Ser No. 547,732, Nov. 18,1955. This application Apr. 24, 1959, Ser. No.

11 Claims. (Cl. 80-6) terials, like soft aluminum alloys, hard stainlesssteels,

titanium, and other materials are diflicult to form with cut threadsWithout tearing the metal but can be readily roll threaded. In suchcases roll threading is also faster.

Because of the advantages that are obtainable, thread rolling has comeinto rather wide spread use as far as external threads are concerned.However, even though the same advantages pertain to internal threads,there is a very limited application of this principle for internalthreads due, primarily, to the lack of simple and efiicient tools forperforming the thread rolling operation.

The present invention provides a tap for this purpose that is easy tomake and maintain, simple to use, and which provides a high degree ofaccuracy and uniformity in the threads produced therewith.

Among the objects of the invention is to provide a thread rolling tap inwhich the thread may be completely formed with one pass of the tap intothe work piece.

It is another object to provide a thread rolling tap in which the threadforming roll or rolls will automatically form a thread of predeterminedpitch regardless of the rate at which the tap is fed into the workpiece.

It is another object to provide a thread rolling tap in which the threadforming roll or rolls include a plurality of annular thread formingribs.

It is another object to provide a tap of the type described in which thethread forming roll or rolls are mounted on pins which are inserted inthe holder at one end thereof in holes which pass completely through theholder so as to permit access to said pins for removing the same fromthe holder.

It is another object to provide a thread rolling tap with a plurality ofthread forming rolls which has a means for limiting deflection of therolls toward each other at each end thereof.

It is another object to provide a thread rolling tap having a pluralityof thread forming rolls, and with at least one of the rolls beingadjustable in its longitudinal position relative to another of saidrolls.

It is another object to provide a thread rolling tap having a pluralityof thread forming rolls, each mounted on a shouldered pin, and with atleast one of the pins being longitudinally positionable by an adjustingscrew whereby the position of the roll on such pin is longitudinallyadjustable with respect to another of said rolls.

It is another object to provide a thread rolling tap comprising a holderwith pins mounted therein and carrying a thread forming rolls, and withmeans for retaining said pins in said holder, the circle circumscribedby said rolls upon rotation of the holder being of larger diameter thanthe diameter of the circles circumscribed by said holder and said pinretaining means, and with the diameter of said circumscribed circle forsaid pin retaining means being no larger than the diameter of saidcircumscribed circle for said holder whereby said pin retaining meanswill not interfere with either chucking of the holder or insertion ofthe tap within a work piece to be internally threaded.

Other objects of the invention will become apparent from the followingdescription and from the drawings in which:

FIGURE 1 is a front view, partly in section along the lines 1il ofFIGURE 2, of a preferred form.

FIGURE 2 is a bottom view of FIGURE 1;

FIGURE 3 is an end view of FIGURE 1;

FIGURE 4 is a view along lines 44 of FIGURE 2.;

FIGURE 5 is a front view, partly in section along the lines 5-5 ofFIGURE 6, showing an optional form with three thread forming rolls andwith means for adjusting the longitudinal position of the rolls;

FIGURE 6 is a bottom view of FIGURE 5;

FIGURE 7 is an end view of FIGURE 6;

FIGURE 8 is a view along the lines 8-8 of FIG URE 5;

FIGURE 9 is a front view partly in section along the lines 99 of FIGURE10 of an optional form employ ing a single thread forming roll;

FIGURE 10 is a bottom view of FIGURE 9;

FIGURE 11 is an end view of FIGURE 9;

FIGURE 12 is a diagram of a typical roller showing a convexconfiguration.

In the form illustrated in FIGURES 1 through 4, the tap comprises aholder 11 having a pair of holes 12 and 13 drilled therethrough from endto end thereof. lAt one end of the holder these holes are enlarged as at14 and 15. Press fitted into the enlargements are pins 16 and 17. Thepin 16 has a collar 18 which abuts the adjacent end of the holder Illand it also has a reduced diameter extension 19 upon which a threadforming roll 20 is rotatably mounted. By continuing the holes 12 and 13completely through the holder from end to end thereof, a rod may beinserted into the holes for knocking out the pins when it is desired toreplace the same.

Likewise, the pin 17 has a collar 21 and a reduced diameter portion 22upon which a second thread forming roll 23 is mounted. The rolls 2G and23 are retained upon the pins 16 and 17 by a plate 24 and screws 25 andZ6 threaded into the outer ends of the pins 16 and 17. The threadforming roll 20 has a series of annular ribs 27 and the roll 23 likewisehas a series of annular ribs 28. These ribs 27 and 2S engage a workpiece 29 for rollforming internal threads therein. The cross sectionalshape of the ribs 27 and 28 conforms with the cross sectional shape ofthe spaces between the threads to be formed and the cross sectionalshape of the spaces between the ribs 27 and 28 conforms with the crosssection-a1 shape of the threads to be formed.

The first one or more ribs on each roll are preferably of smallerdiameter than the others to facilitate starting of the roll into thework piece.

The axis 32-492 of the hole 12 is parallel with the axis 33-413 of theholder as viewed in FIGURE 1 and is at an angle 35 'with the axis 3333as viewed in FIGURE 2. In other words, the axis 3232 is parallel withthe axis of the holder in one plane and is at an angle 35 in anotherplane at right angles to the first mentioned plane.

The end of the holder adjacent the thread rolls is formed with a surface40 which is perpendicular to the axis 32- 32.

In like manner, the axis 4141 of the allel with the hole 13 is paraXis33-33 of the holder as viewed in 3 FIGURE 1 and is at an angle 43 withthe axis of the holder as viewed in FIGURE 2. The surface 45 isperpendicular to the axis 4141. The angles 35 and 4 3 are equal to eachother and are also equal to the helix angle of the thread to be formedin the work piece 29.

The outer diameter 47 of the holder 11 is smaller than the minordiameter of the threads to be formed in the workpiece so that the holdermay enter the work piece if it is so desired.

The roller 29 is rotatable on the pin extension 19 about the axis 32-32and the roller 23 is rotatable on the extension 22 about the axis 41-41.

The annular ribs 27 and 28 on the rolls are offset longitudinally withrespect to each other an amount equal to one half the pitch of thethread to be formed.

In the modification shown in FIGURES through 8 there is a work holder 66having three longitudinal holes 61, 62, and 63. The longitudinal axes ofthese holes are equidistant from the axis of the holder 60 in anytransverse plane perpendicular to the axis of the holder, and theangular spacing of the holes about the axis of the holder is also equal.Mounted in the hole 63 is a pin 64 having a groove 65 adjacent its innerend and having a collar 56 abutting the adjacent end of the holder 66.Outwardly of the collar 56 is a reduced diameter 57 upon which ismounted a thread forming roll 68. Adjacent the outer end of the pin 64is a groove 69. Mounted in the holes 61 and 62 are pins 66 and 67 withlike grooves, collars, and reduced diameters as on pin 64, and withthread forming rolls 70 and 71 rotatably mounted on their outer ends.

The holder 69 has an annular groove 73 which intersects the holes 61,62, and 63. Mounted in this groove 73 is a split ring 74. The ring 74projects into the grooves 65 formed on each of the pins 64, 66, and 67for retaining the same within the holes 61, 62, and 63. At the innerends of the holes 61, 62, and 63, there are threaded sections 75, 76,and 77 into which adjusting screws 78, 79, and 80 are threaded.interposed between the adjusting screws and the corresponding pin areballs 81', 82, and 83. The adjusting screws, acting through the balls,permit direct adjustment of the longitudinal position of the pins andhence of the rolls so that the rolls may be adjusted longitudinally ofeach other for precise positioning thereof with respect to each other intheir proper longitudinal offset. Mounted in the grooves 69 and betweenthe three pins 64, 66, and 67 is a circular disk 34 which supports theends of the pins to prevent deflection toward each other during thethread forming operation.

The grooves 65 are wider than the ring 74 and the disk 84 is slightlynarrower than the grooves 69 so as to permit the longitudinal adjustmentof the roll carrying pins 64, 66, and 67 with respect to each other.Preferably, the pins 64, 66, and 67 are initially inserted with theirrespective collars 56 against the adjacent end face portion of theholder 60 and with the adjusting screws 78, 79, and 80 slightlyretracted. Any inaccuracy in the longitudinal positioning of any of therolls 68, 70, and 71 with respect to each other is then corrected bymoving the respective pin 64, 66, or 67 outwardly of the holder by meansof the corresponding adjusting screw 78, 79, or 80. In such case thecollar 56 of the adjusted pin will be moved slightly away from thecorresponding end face of the holder 60 and inward movement of the pinwill then be limited by the corresponding ball 81, 82, or 83 and theassociated adjusted screw.

It will be noted that the split ring 74 which retains the pins in theholder is no larger in diameter than the holder, or in other words, acircle circumscribed by the ring 74 as the holder rotates on itslongitudinal axis has a diameter no larger than the diameter of a circlecircumscribed by the holder. Likewise, the rolls 68, 70, and 71 projectradially beyond both the holder 60 and retainer ring 74 so that thecircle circumscribed by said rolls as the holder rotates has a diametergreater than the diameters of circies circumscribed by said holder andsaid ring 74. This results in an efficient structure in which the pinretaining ring 74 does not interfere with chucking of the tool in asuitable chuck and also permits entrance of the rolls into a work pieceto any depth without interference from the holder or retainer ring.

The circular disk 84 is preferably notched in three places as at 89 forreceiving the reduced portions of the pins which form the bottoms of thegrooves 69. Such notches 89 not only support the ends of the pinsdirectly against deflection radially inwardly of the holder, but alsoangularly with respect to the axis of the holder.

The thread forming rolls 68, 7t and 71 each have annular ribs such asshown at 85. These ribs are longitudinally offset from each other adistance equal to one third of the pitch of the thread to be formed.

As in the case of the two-roller form shown in FIG- URES 1 through 4,the longitudinal axis of each thread forming roll is parallel with theaxis of the holder in one plane and is at an angle with the axis of theholder in a second plane at right angles to the first mentioned plane.

In the modification shown in FIGURES 9 through 11, there is shown aholder 90 having but a single hole 91 therethrough, this hole having anenlargement 92 at one end thereof. Press fitted within the enlargement92 is a pin 93 having a collar 94 in engagement with the adjacent end ofthe holder. Beyond the collar there is a reduced diameter portion 95upon which a work roll 96 is rotatably mounted and which is retainedthereon by a screw 97 threaded into the outer end of the pin 93. Theroll 96 has annular ribs 98 formed thereon.

As in the case of the previously described forms, the axis of the roller96 is parallel with the axis of the holder in one plane and is at anangle with the axis of the holder in a second plane which is at rightangles to the first men tioned plane.

In operation, the two-roller form shown in FIGURES 1 through 4 and theworkpiece 29 may be mounted ina suitable machine tool (not shown) forrotation relative to each other. The holder 11 is then advanced towardthe work piece. The work piece will previously be formed with a hole 30of a diameter closely equal to the pitch diameter of the thread to beformed therein. As the holder 11 is advanced, the rolls 2t and 23 willenter the work piece and form the thread. During this part of theoperation the rolls 2t) and 23 will be rotated on their own aXeS byfrictional contact with the work piece 29. When the thread is formed tothe proper depth within the work piece 2 9, rotation of the holder isreversed and the rolls will unthread themselves from the work piece.

Operation of the three-roller and single-roller forms is similar to thatof the two-roller form and a further description of the same is notthought necessary.

The axis of the holder 11 is coincident with the axis f the work piece29 and since the axis of the roller 20 is at an angle 35 with the holderin one plane, it will likewise be at an angle 35 with the axis of thework piece in one plane. From this it is apparent that as the rollerenters the hole 30, the first and last of the ribs 28 will tend to forma deeper thread impression in the work piece than will the rib 28 in thecenter of the roller 20. The same is true of the other roller 23 and ofthe rollers shown in the other forms of the invention.

The larger the diameter of the thread to be rolled with respect to thepitch of the thread, the more insignificant will be this effect and insome instances the effect can be disregarded. When it is desired thatall of the ribs in the rollers make the same impression in the Workpiece, the rollers may be formed in band shape as shown in FIG- URE 12.The radius R can be approximated closely enough for practical purposesby the formula:

Rradius of roller at pitch diameter of annular ribs.

L-length of roller (vertical plane through axis of roller intersectsvertical plane through axis of thread midway along length of roller).

P-pitch diameter of finished thread.

6helix angle of pitch diameter of thread.

Barrel shaping in this manner so that all, or at least a plurality ofribs on the rollers make the same impression in the work piece resultsin a burnishmg of threads in the work piece by the succeeding ri-bsandresults in more uniform sizing of the thread and in an improvedfinish thereon.

Although only single, double, and three-roller forms have beenillustrated and described in detail, it is obvious that any desirednumber of rollers may be provided. However, in each case it is necessarythat the axis of each of the rollers be parallel to the axis of theholder 111 one plane and at an angle equal to the helix angle of thethread in another plane at right angles to the first mentioned plane,and that the ribs on the rollers be longitudinally offset from eachother an amount equal to that proportion of the thread pitchcorresponding to the angular spacing between the rollers. Modificationsmay be made in various details of construction without departing fromthe scope of the invention as defined in the following claims.

This application is a continuation of my prior co-pending applicationSerial Number 547,732, now abandoned, filed November 18, 1955.

I claim:

1. A tap for rolling internal threads comprising a holder, at least twopins mounted on said holder, a thread forming roll rotatably mounted oneach pin, a shoulder on at least one of said pins against which therespective roll abuts, the axes of the rolls being spaced from the axisof the holder and parallel thereto in one plane and at an angle theretoin another plane, and screw means for engaging and moving said one pinlongitudinally for ad usting the longitudinal position of said one pinon said holder whereby said shoulder will adjust the longitudinalpos1t1on of the roll thereagainst with respect to another of said rolls,the circle circumscribed by the adjusting means upon rotation of theholder on its longitudinal ax1s being smaller than the circlecircumscribed by the rolls upon said rotation.

2. A tap for rolling threads comprising a holder, three or more pinsextending from the extreme end of the holder, a thread forming rollrotatably mounted on each pin, the axis of each roll being parallel tothe axis of the holder in a first plane and at an angle thereto nanother plane, each pin having an integral portion pro ect ng beyond therespective roll and having a groove in said projecting portion, thebottom of each groove constituting a reduced end portion of each pin,and a circular disk between said pins having a diameter less than thediameter of a circle which passes through the axis of the pins, saiddisk having arcuate notches therein to receive the reduced end portionof said pins and thus be seated in said grooves for supporting the endsof the pins against deflection toward the axis of the holder, saidgroove retaining the circular disk against axial displacement.

3. A tap for rolling internal threads in a bore of a workpiececomprising a holder, said holder at one end having a radially outersurface adapted to be gripped by a rotatable device whereby said holdermay be rotated, a plurality of longitudinally extending openings in saidholder toward the other end thereof, the longitudinal axis of eachopening being spaced from the longitudinal axis of the holder andparallel thereto in one plane and at an angle thereto in another plane,a pin mounted in each opening, the inner end of each pin being housedcompletely within said holder and terminating short of said one end ofthe holder whereby each pin is inaccessible for driving connection withsaid rotatable device, each pin carrying a thread forming means adaptedto enter the bore of said workpiece, means for retaining said pinswithin said openings, the diameter of the circle circumscribed by saidthread forming means upon rotation of said holder being greater than thediameter of the circle circumscribed by said retaining means and alsobeing greater than the diameter of the circle circumscribed by saidother end of said holder whereby said tap may enter said workpiecewithout interference from said retaining means or said holder.

4. A tap for rolling internal threads in a hollow workpiece, comprisinga holder adapted to enter said workpiece and to be rotated about alongitudinal axis, at least two pins mounted on the holder at one endthereof and rotatable with said holder about said longitudinal axis, athread forming roll rotatably mounted on each pin and adapted to form aninternal thread in said workpiece, the axes of the rolls being spacedfrom the axis of the holder and parallel thereto in a first plane and atan angle thereto in another plane, means for fixing the longitudinalposition of one of said rolls with respect to said holder, means foradjusting the longitudinal position of the other of said rolls withrespect to said one of said rolls, said adjusting means being locatedwholly within the radial confines of said holder and rotatabletherewith.

5. A tap in accordance with claim 4 in which there is a means rotatablewith said holder and independent of said adjusting means for retainingsaid pins on said holder, said retaining means likewise being containedWholly within the radial outline of the holder.

6. A tap for rolling internal threads in a bore of a workpiececomprising a holder, said holder at one end having a surface adapted tobe gripped by a rotatable device whereby said holder may be rotated, aplurality of longitudinally extending openings in said holder toward theother end thereof, the longitudinal axis of each opening being spacedfrom the longitudinal axis of the holder and parallel thereto in oneplane and at an angle thereto in another plane, a pin mounted. in eachopening, the inner end of each pin being housed within said holder forprotecting the same, each pin carrying a thread forming means adapted toenter the bore of said workpiece, means for retaining said pins withinsaid openings, the diameter of the circle circumscribed by said threadforming mean-s upon rotation of said holder being greater than thediameter of the circle circumscribed by said retaining means and alsobeing greater than the diameter of the circle circumscribed by saidother end of said holder whereby said tap may enter said workpiecewithout interference from said retaining means or said holder, saidretaining means comprising a ring carried within an annular groove insaid holder and encircling said pins.

7. A tap for rolling internal threads in :a hollow workpiece comprisinga holder, at least two pins journaled in the holder and projecting fromone end thereof, a thread forming roll rotatably mounted on each pin andadapted to enter a hollow workpiece, means on at least one pin fixingthe longitudinal position of the roll thereon, the axes of the rollsIbeing spaced from the axis of the holder and parallel thereto in afirst plane and at an angle thereto in another plane, and means carriedby said holder for moving said one of the pins axially in its journalwith respect to another of said pins for adjusting the longitudinalspacing of the roll on said one pin with respect to the other rolls,means independent of the adjusting means for retaining the pins withinthe holder, said retaining means comprising a split ring carried withina groove in said holder and fitting loosely Within a groove in said oneof said pins for permitting said axial movement of said one pin by saidadjusting means.

8. A tap for rolling internal threads comprising a holder, at least twopins mounted on said holder, a thread forming roll rotatably mounted oneach pin, a shoulder on at least one of said pins against which therespective roll abuts, the axis of each roll being spaced from the axisof the holder and parallel thereto in one plane and at an angle theretoin another plane, adjusting means for engaging and moving said one pinlongitudinally for adjusting the longitudinal position of said one pinon said holder whereby said shoulder will adjust the longitudinalposition of the roll thereagainst with respect to another of said rolls,the circle circumscribed by the adjusting means upon rotation of theholder on its longitudinal axis being smaller than the circlecircumscribed by the rolls upon said rotation.

9. A tap for rolling internal threads comprising a holder adapted to berotated about a longitudinal axis, a bore in said holder extendinglongitudinally thereof, a pin having one end extending into said bore,the axis of said pin being spaced from said longitudinal axis andparallel thereto in a first plane and at an angle thereto in anotherplane, a thread forming roll rotatably mounted on the other end of saidpin, said holder having an annular groove in its outer peripheryintersecting said bore, said pin having an annular groove therein inregister with said annular groove in said holder, and a ring mountedwithin the annular groove in said holder and projecting into the annulargroove in said pin and serving to retain said pin within said holder.

10. A tap for rolling internal threads in a bore of a workpiececomprising a holder, said holder at one end having a surface adapted tobe gripped by a rotatable device whereby said holder may be rotated, aplurality of longitudinally extending openings in said holder toward theother end thereof, the longitudinal axis of each opening being spacedfrom the longitudinal axis of the holder and parallel thereto in oneplane and at an angle thereto in another plane, a pin mounted in eachopening, the inner end of each pin being housed within said holder forprotecting the same, each pin carrying a thread forming means adapted toenter the bore of said workpiece, means for retaining said pins withinsaid openings, the diameter of the circle circumscribed by said threadforming means upon rotation of said holder being greater than thediameter of the circle circumscribed by said retaining means and alsobeing greater than the diameter of the circle circumscribed by saidother end of said holder whereby said tap may enter said workpiecewithout interference from said retaining means or said holder, saidretaining means being located between said rolls and said one end of theholder.

11. A tap for rolling internal threads comprising a holder adapted to berotated about a longitudinal axis, an opening in said holder extendinglongitudinally thereof, a pin having one end extending into saidopening, the axis of said pin being spaced from said longitudinal axisand parallel thereto in a =first plane and at an angle thereto inanother plane, a thread forming roll associated with said pin, saidholder having an annular groove in its outer periphery intersecting saidbore, said pin having an annular groove therein in register with saidannular groove in said holder, and a ring mounted within the annulargroove in said holder and projecting into the annular groove in said pinand serving to retain said pin within said holder.

References Cited in the file of this patent UNITED STATES PATENTS885,068 Moy Apr. 21, 1908 2,145,587 Draper Ian. 31, 1939 2,349,863Hallberg May 30, 1944 2,645,954 Pfingston July 21, 1953 2,720,801Erdelyi Oct. 18, 1955

